Answer this question truthfully
### Question: What Causes Yersinia Pestis Infection?
### Response: Plague is caused by the bacteria Yersinia pestis. Rodents, such as rats, carry the disease. It is spread by their fleas.
The plague bacteria can be transmitted to humans by the following ways:
Flea bites
Plague bacteria are most often transmitted by the bite of an infected flea. During plague epizootics, many rodents die, causing hungry fleas to seek other sources of blood. People and animals that visit places where rodents have recently died from plague are at risk of being infected from flea bites. Dogs and cats may also bring plague-infected fleas into the home. Flea bite exposure may result in primary bubonic plague or septicemic plague.
Contact with contaminated fluids or tissues
Humans can become infected when handling tissue or body fluids of a plague - infected animal.
Infectious droplets
When a person has plague pneumonia, they may cough droplets containing the plague bacteria into the air. If these bacteria -containing droplets are breathed in by another person, they can cause pneumonic plague. Typically this requires direct and close contact with the person with pneumonic plague. Transmission of these droplets is the only way that plague can spread between people.
This type of spread has not been documented in the United States since 1924, but still occurs with some frequency in developing countries. Cats are particularly susceptible to plague and can be infected by eating infected rodents. Sick cats pose a risk of transmitting infectious plague droplets to their owners or to veterinarians. Several cases of human plague have occurred in the United States in recent decades as a result of contact with infected cats.
In the Middle Ages in Europe, massive plague epidemics killed millions of people. Plague can still be found in Africa, Asia, and South America. Today, plague is rare in the United States, but it has been known to occur in parts of California, Arizona, Colorado, and New Mexico.
The three most common forms of plague are:
Bubonic plague -- an infection of the lymph nodes Pneumonic plague -- an infection of the lungs Septicemic plague -- an infection of the blood
The time between infection and development of symptoms is typically 2 to 7 days, but may be as short as 1 day for pneumonic plague. Risk factors for plague include a recent flea bite and exposure to rodents, especially rabbits, squirrels, or prairie dogs, or scratches or bites from infected domestic cats.